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Fun fact: during the 1960s, the ACC regulated class by length at waterline. In order to cheat the system, boat designers would give their sailboats long stern overhangs, which reduced the length at waterline. But when they started sailing, the heel would cause that overhang to dip into the water, and caused the length at waterline to increase, thus increasing hull speed. It's because of this that long stern overhangs seem to be the "classic" 1960s design

@markandoyo2204

Жыл бұрын

Although this historical disclosures were also evident from that time were the oldschools became the most memorable classic signatures wayback from that glory of era, as these time that the vessels became more and more advance that the waterline length with overall lenght draft by the small vessel players were having the key reasons to take parallel length seriously achieves high priority especially the Sail clothes achieves zero porosities and whilst the sail size needs wide base to maximise the stability even this is too critical to be complied trans-oceangoing seaworthiness

The formula results from the propagation speed of a wave with the same wavelength as the boat''s length (The boat will make a disturbance on the water surface that is roughly of the same size as its own length) in deep water c = sqrt(g L/(2*pi)). The factor 1.34 comes from the magnitude of gravitational acceleration and appropriate unit conversion factors. For example, 1 foot/1 m = 0.3048, g=9.81 m/s^2 and (1 knot) / (1 m/s) = 0.514444.

@ImproveSailing

3 жыл бұрын

Thanks Guillermo for explaining the physics. I have pinned this comment for others as well.

Great video, thank you! I sailed for 30 years before I learned how a sail really works. I had just bought a Supercat 17 and I bought a catamaran racing book. The book explained how the sail is a vertical wing creating lift just like an airplane wing. So the sailboat is moving forward due to the lift generated on the downwind side! The boat is getting sucked forward!! How crazy is that??

Did a great job of keeping it not too technical but highly informative

@ImproveSailing

3 жыл бұрын

Thanks Joe, I appreciate your comment.

@liquidlemon3335

Жыл бұрын

@@ImproveSailing so, how do I find the hull speed of a non existent boat?

This formula is only rough guide to old designs of displacement sailing boats..... Newer sail boat designs ( flatter bottom ) are created so that sailing boat going upwind is behaving like displacement boat ( and that formula can apply ) , BUT going downwind they can easily TRIPLE the speed of this formula..... That is the reason why designers MUST supply you with speed diagram of different points of sailing ( polar diagram). Of course as Michael has previously commented this formula can't be applied to all multi hulls ( catamarans, trimarans, proas) and especially nowadays new foiling designs.... Thanks for posting....

@ImproveSailing

4 жыл бұрын

Thanks for sharing your knowledge. I agree, especially the hydrofoils are A LOT faster. They also look cool ...

@IWLDELJ

4 жыл бұрын

I've been working on some spreadsheets off and on for a few years that give a generic, yet more accurate idea of a sailboat's speeds. I've been working toward having it work for mutihulls as well. Your comment just sparked an idea to have different speeds for upwind and downwind... But that may be over my head.

3:51 is what you came for

I enjoyed the Calculus, Geometry and Physics lecture. I have found most of the information on the internet is like getting a weather forecast. Everyone repeats what they have heard; no one verifies the facts or even knows what the facts are. Allow me to ask you a simple physics question; take two round objects the same length and size, both have the same nose cone similar to a jet aircraft. Object A; starts the gradual curve to the end (tail/stern) point at 50% of the length. Object B; starts the gradual curve to the end (tail/stern) point at 75% of the length. Simple Question: which object is faster given everything else is constant; Object A or Object B. Last question what is making Object A or B slower given everything else is the same (constant)?

could you do a short video with some of your infgraphics in various bits of sailing you have covered in dutch as i am trying to learn some dutch. i need simple ie sail = etc..thanks.

@ImproveSailing

3 жыл бұрын

Cool idea, I'll look into it (I don't promise anything though)

My question is about that formula. It seems that two boats of equal length at waterline with completely different beam width at waterline will have the same top speed? I feel the beam width would cause some drag and is causing more displaced water slowing the wider boat. Is there something I am missing?

@slooob23

6 ай бұрын

You're correct, it just means that some hull forms will require less energy to reach their hullspeed than others. Hull speed is simply the theoretical limit of a given hull length on waterline. Other design considerations will affect the average speed of a given sailboat up to that limit thus making one boat faster than another on average speed.

as we sail the apparent lateral resistance changes ... it moves forward at speed ...

You do not need any surfing conditions to exceed hull speed. You just need to get more force into the boat. The problem with sailboats is that more force means more rolling over to the lee side of the boat and more slipping of the wind over your sails. A heavier keel could do, a ballast system and ballast at luv could do, even a more rectangular shape of the hull could do. But .. a heavier keel means more depth and more friction, also does a more rectangular shape in terms of friction. The ballast system is a good way but expensive. If your mast, sails and ropes can withstand the force you can exceed the hullspeed of your boat by setting more sails with winds from aft. The hullspeed is just a point were the force to move your boat and the shape (mostly length) of your hull is at the optimum.

the keel as i said should be at the nose or a rod forward with a small rudder 20 ft infront of boat makes virtual keel allows into the wind and beyond sailing .. yes sailing counter wind

Does this theory also apllies to motor boat? Let say, boat A and B have same hull design and boat engine. But boat A have longer hull / LWL. Longer boat usually means more weight.. Will the boat A be faster than boat B? What is the advantage of making longer boat?

@ivarlaupet8972

4 жыл бұрын

Aditya Ali Hull speed is not an upper limit, but it requires a lot of force (bigger engine) to go faster than the hull speed. The main advantage of a longer hull is that the boat will go over the waves instead of going through them.

@tycondero1647

3 жыл бұрын

Yes, it perfectly applies to any boat in which the hull moves through the water. Whether it has an engine or not doesn't matter. A longer/slender designed hull with the same total displacement of a boat that has a wider and shorter hull will attain a greater maximum speed with the same amount of power (whether it is wind or engine powered does not matter) applied to it due to both the water friction/resistance and the hull speed limit. Also weight doesn't impact a boat as much as people tend to think. Weight impacts the acceleration and depending on the draught can impact the amount of water resistance and thereby maximum speed of a ship, however usually you need to add a lot of weight to significantly increase the draught to affect this. As long as you move through the water below the hull speed limit it will not be of much benefit to change anything hull design wise. However, once you want to go over the hull speed limit you really need to start thinking of cleverly improving/designing your hull and/or improving power input.

@recurrenTopology

2 жыл бұрын

The above answers are somewhat correct, but most modern recreational motorboats are designed to plane (or semi-plane) once at speed. That means they are no longer displacement vessels (moving an amount of water roughly equivalent to their static displacement) but are instead lifted out of the water by the flow of water over their hulls. Once planning, the boat is no longer in a regime in which hull speed has much bearing, and they are able to obtain a far higher speed at equivalent power than they would have as displacement vessels. An extreme example of this is with foiling craft, which have effectively zero displacement once up on the foil, but even with your run-of-the-mill bowrider motorboat you can easily see that at speed it is essentially skipping across the top of the water rather than pushing through. With regards to weight, for planing vessels lower weight is rather important since it means that less power needs to be converted to lift, and the boat is able to start planing at a lower speed. This is why high performance hydroplanes and foil craft are so concerned with being as light as possible.

i never thought of thys b4 either well not the nose pieces the apparent clr at speed deltasz

With the boat plays no part in whole speed?

having a sail 20 feet trailing will also allow for more speed and higher pointing angle

I think the formula is a bit off. It says that the theoretical max speed of a 100 ft boat is 13.4 kts but modern 100 ft racing boats can do close to 40. I'm not sure what causes the discrepancy but I think it might be that the boat starts to plane on the water like a powerboat. I think the practical reason that longer boats are faster is because the boat has more time to push the water out of the way and thus less drag. i.e. if the widest part of the boat is the midpoint, then on a 100 ft boat, it has a 50 ft range to push the water to the side whereas a 50 ft boat would only have 25 ft. Anyway, I thought it was a good video. :)

@ImproveSailing

3 жыл бұрын

Thanks Kenton, appreciate it. I think you're right, altough that is not a pure displacement hull. I also know that a lot of high performance racers use hydrofoil keels, which is also cheating in a way.

I've got a cutter boat from 1922, no manual about the speeds sadly 🙊

its easier to break hull speed than you think, i sailed across lake ontario in a j35 and our max speed was 14knts

@slooob23

6 ай бұрын

Did it have the kite up and was it planing?

Hydrofoils kind of negate hull speed. Plus what about planing?

@permanenceinchange2326

Жыл бұрын

Of course, but this is about traditional keel boats, of which the hull stays in the water. I sail a very small Europe, and it's planing all the time. If it were not, it was going very slow!

you can make a flexible hu;;; that is long and curved and then point into the wind more .. the hull flex and vibe does what? virtual hull resistance factor

Longer boats makes sails faster (check) Kindly check from the other findings that the extensive research on the hands of Hydrodynamics, ballasting, sail match can be counted regardless of short vessels with bigger sails, the trimmed of the vessels and the counteractive its defined waterline base into the complete stability platforms and the complete Physics were the another accountable fast sailboats although the shorter sailboats with Keel oriented can withstand longer in the battles of seaworthiness routes and they can keep at the most turbulent sea currents but they cannot take any fast sails as due to the geometrical round bottoms as though another feasible facts that the oversized sails much needed flat bottom boats and the required longer lengths can be a true factual basis but having additionally either to mount with Centerboards, Daggerboards and the ballast displacements are the significant hydrodynamic basis and the correct applications in Science in terms of arms race and space edge Sportscraft but limits its trans oceangoing seaworthiness.

Noise

Nothing new here, 1.4 times the squareroot of the water length in feet is the max speed in knots. This applies even to war ships. A typical frigate with waterline length of 400 feet has a max speed if 28 knots. Yes, they can a bit faster with a huge increase in HP. But can't carry enough fuel to go very far at flank speed. Unless you can plane. T

boats should be banded not round for counter wind sailing .. round works on land .. on water round slidesz .. on water angles work better ... sailing 101

@permanenceinchange2326

Жыл бұрын

Every hull design consists of a compromise between speed, stability and manouverability. Which choises the designer makes depends on the type of boat, of which one of the main factors imho is whether the hull should be planing or not. It's not that straight as you suggest... sailing Europe Dinghy

Catamarans destroy the speed limit sooooo ..1.34 goes no where near it ...

@ImproveSailing

4 жыл бұрын

Yes that's absolutely right, cats are just great. They lie higher in the water if I understood correctly.

@gerritgovaerts8443

3 жыл бұрын

@@ImproveSailing not all cats are immune to max hull speed caused by the bow wave , but performance cats (Outremer , Gunboat , DazCat , Marsaudon Composites ) with very slender hulls (>>12 : 1 length to beam ratio) are virtually freed of this limit on speed . Your typical production charter cat (Lagoon, Leopard , Fountan Pajot etc..) has pretty bulky hulls with a ratio between 8 to 10:1 and are still affected by max hull speed to a certain extent

@Hugh_Jarsole

3 жыл бұрын

The reason for that is that a cat has two hulls, effectively doubling the LWL in relation to the actual length of the boat, so a 30ft cat has the effective LWL of a 60ft monohull. Of course there's variables, and it's never as clean and precise as that, but I'd wager thats a big slice of the pie. Same formula applies, but double🙂

@recurrenTopology

2 жыл бұрын

@@Hugh_Jarsole It is my understanding that it is not the multi-hull nature of cats that allows them to have drastically lower wave-making resistance, but is instead the result of the wave-piercing nature of their hulls. Being narrow and having low forward buoyancy the cats hulls are able to cut through waves and so are far less impeded by the high bow wave induced at hull speed. A mono-hulled boat with an equivalent wave-piercing design would have the same lowered wave-making resistance, such as seen on a racing kayak, for example.

@Hugh_Jarsole

2 жыл бұрын

@@recurrenTopology that makes sense as well, but would it not be a combination of the two? I would think the math would still carry with two hulls🤔 now I'm gonna be researching the physics of catamarans all night 😂

hull speed is not max speed limit it is drag coefficeint of boat hull ... wich has to be nromalized way more .. wow naval engineering is way behind carsz

thye are not faster its yoru same rocket nonsense legth over width is thrust ... width is more resistanc ein water but not above it ... length is time in water width is time out of it

Longer boats are faster because they have bigger sails.

I enjoyed the Calculus, Geometry and Physics lecture. I have found most of the information on the internet is like getting a weather forecast. Everyone repeats what they have heard; no one verifies the facts or even knows what the facts are. Allow me to ask you a simple physics question; take two round objects the same length and size, both have the same nose cone similar to a jet aircraft. Object A; starts the gradual curve to the end (tail/stern) point at 50% of the length. Object B; starts the gradual curve to the end (tail/stern) point at 75% of the length. Simple Question: which object is faster given everything else is constant; Object A or Object B. Last question what is making Object A or B slower given everything else is the same (constant)?